Structure of first arm of industrial robot having articulated horizontal arms

ABSTRACT

Provided is a compact first arm (12) of an industrial robot having articulated horizontal arms, which first arm has a direct drive motor (19), an electromagnetic brake (25), and a rotary encoder (34, 36) disposed close to each other concentrically between the first arm (12) and a base post (10) supporting the first arm (12), and has another direct drive motor (39), another electromagnetic brake (45), and another rotary encoder (54, 56) disposed close to each other concentrically between the first arm (12) and a second arm (14) rotatably supported by the first arm (12).

TECHNICAL FIELD

The present invention relates to a structure of the first arm of anindustrial robot having articulated horizontal arms, particularly to thestructure of the first arm having a direct drive motor, etc., builttherein to realize a compact unit.

BACKGROUND ART

An industrial robot having articulated horizontal arms usually comprisesa vertical post fixed to a floor, a first arm rotatably attached to thepost, a second arm rotatably attached to the first arm, and a wristportion attached to an end of the second arm, which wrist portionrotatable and can move linearly. Of course, other industrial robotshaving articulated horizontal arms exist, such as a robot whichcomprises an inner trunk body movable upward and downward on the base ofthe vertical post, the first arm being rotatably attached to the innertrunk body, but an indirect drive motor driving through a transmissionmechanism may be adopted as a drive motor for the first arm or thesecond arm in such an industrial robot having articulated horizontalarms. When a direct drive motor is adopted, a robot does not necessarilyhave a compact structure, since it must be equipped with a brake unitand a rotation position detector.

DISCLOSURE OF THE INVENTION

Accordingly, an object of the present invention is to solve the aboveproblems by disposing direct drive motors, brake units, and rotationposition detectors for the first and second arms in a compact form inthe first arm, to make the robot compact.

In view of the above-mentioned object, the present invention provides astructure of a first arm of an industrial robot having articulatedhorizontal arms, characterized in that a first direct drive motor isdisposed at one end of the first arm coaxially with a first central axisthereof for rotating the first arm, that a first brake means and a firstrotation position detector means coaxial with the first central axis arejuxtapositioned adjacent to the first direct drive motor, that a seconddirect drive motor is disposed at the other end of the first armcoaxially with a second central axis thereof for rotating a second arm,which second arm can rotate on the base of the first arm, and that asecond brake means and a second rotation position detector means coaxialwith the second central axis are juxtapositioned adjacent to the seconddirect drive motor.

The structure is made compact by a juxtaposition of the coaxial rotationposition detector means and the brake means adjacent to the direct drivemotor. Therefore, the industrial robot having articulated horizontalarms can be made compact so that the possibility of interference with anapparatus or an object to be handled in an operating region can bereduced.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 a partial longitudinal sectional view of an industrial robothaving articulated horizontal arms, one of the arms having a structureaccording to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail hereinafter accordingto the embodiment shown in the attached drawing. An industrial robothaving articulated horizontal arms comprises a vertical post 10 fixed toa floor, a first arm 12 rotatably mounted on the vertical post 10 andable to rotate around a vertical axis θ, a second arm 14 rotatablyattached to one end portion of the first arm 12 and able to rotatearound a vertical axis u and a wrist portion 16 attached to one endportion of the second arm 14, which wrist portion can rotate around avertical axis α and move upward and downward along the axis α.

Now a structure for rotating the first arm 12 around the axis θ will bedescribed. The first arm 12 is attached to the top of the vertical post10 through a bearing 38 to enable a precise rotation thereof, and adirect drive motor 19 is disposed around the axis θ at a lower portionadjacent to the bearing 38. An armature 20 of the motor 19 is fixed tothe vertical post 10, and a magnet 22 of a magnetic field pole is fixedto the first arm 12 through a yoke 24. An electromagnetic brake 25 isjuxtapositioned adjacent to the motor 19 at a lower portion, andexciting pole 26 is fixed to the vertical post 10. The exciting pole 26causes a brake shoe 28 to retract from a friction drum 30 fixed to thefirst arm 12, by an electromagnetic force thereof, during operation ofthe first arm 12. The above-mentioned yoke 24 and the friction drum 30are integrated as one body because the motor 19 and the electromagneticbrake 25 are positioned close to each other in this embodiment.

A rotary plate 34 of a rotary encoder is fixed to a hollow cylindricalshaft 32 extending from the first arm 12 and vertically projecting intoan inside of the vertical post 10 so that a central axis thereofcoincides with the above-mentioned axis θ. On the other hand, astationary plate 36 is fixed to the upper portion of the inside of thevertical post 10 corresponding to the rotary plate 34.

According to the above-mentioned structure, the first arm 12 can berotated around the axis θ, and the rotation thereof can be controlled.Furthermore, electrical lead wires and working fluid tubes for a robothand can be disposed at the end of the first arm 12 through the hollowcylindrical shaft 32 and a cover 18 from a hole 60 at a lower portion ofthe vertical post.

A structure for rotating the second arm 14 around the axis u will bedescribed hereinafter. A hollow cylindrical portion 62 is projected fromthe bottom end of the second arm 14, and rotatably mounted on the endportion of the first arm 12 through a bearing 58. A central axis of thehollow cylindrical portion 62 coincides with the axis u. Another directdrive motor 39 for the second arm is attached to a lower outer surfaceof the hollow cylindrical portion 62. An armature 40 of the motor 39 isfixed to the lower outer portion of the hollow cylindrical portion 62,and a magnet 42 of a magnetic field pole is fixed to the first arm 12through a yoke 44. Another electromagnetic brake 45 is juxtapositionedat a position just above the motor 39, and exciting pole 46 is fixed tothe hollow cylindrical portion 62. The exciting pole 46 causes a brakeshoe 48 to retract from a friction drum 50 fixed to the first arm 12 byan electromagnetic force thereof during operation of the second arm 14.The yoke 44 and the friction drum 50 are integrated as one body also inthis portion, because the motor 39 and the electromagnetic brake 45 arepositioned close to each other. A rotary plate 54 of a rotary encoderfor detecting a relative rotation position of the second arm 14 withrespect to the first arm 12 is fixed to a hollow cylindrical shaft 52vertically projected on the first arm 12 and extended into the hollowcylindrical portion 62 so that the central axis thereof coincides withthe aforementioned axis u. On the other hand, a stationary plate 56 isfixed to an upper portion of an inside of the hollow cylindrical portion62 corresponding to the rotary plate 54.

The second arm 14 can rotate around the axis upon the base of the firstarm 12 and the rotation thereof be controlled, and lead wires and tubescan be disposed inside the second arm 14 through the hollow cylindricalshaft 52, according to the above-mentioned structure.

As apparent from the foregoing description, an industrial robot can beconstructed in a compact form whereby drive units for driving the firstarm and the second arm are disposed in the first arm according to thepresent invention. Furthermore, interference with an apparatus or anobject to be treated in a working area can be reduced.

We claim:
 1. A structure of a first arm of an industrial robot havingarticulated horizontal arms, characterized in that a first direct drivemotor having a yoke is disposed at one end of said first arm coaxiallywith a first central axis thereof for rotating said first arm, that afirst drum type brake means having a drum integrated with said yoke ofsaid first motor adjacent said brake and a first rotation positiondetector means coaxial with said first central axis are juxtapositionedadjacent to said first direct drive motor, that a second direct drivemotor having a yoke is disposed on the other end of said first armcoaxially with a second central axis for rotating said second arm, whichsecond arm can rotate on the base of said first arm, and that a seconddrum type brake means having a drum integral with said yoke of saidsecond motor adjacent to said second brake and a second rotationposition detector means coaxial with said second central axis arejuxtapositioned adjacent to said second direct drive motor.
 2. Astructure of a first arm of an industrial robot having articulatedhorizontal arms according to claim 1, wherein a rotary plate, which isone element of said first rotation position detector means, is attachedto a projecting portion projecting from said first arm into an inside ofa base part supporting said first arm, and wherein another rotary plate,which is one element of said second rotation position detector means isattached to another projecting portion projecting from said first arminto an inside of said second arm.
 3. A structure of a first arm of anindustrial robot having articulated horizontal arms according to claim2, wherein said projecting portion and said another projecting portionhave a hollow structure, whereby lead wires and tubes, etc., passedthrough said first arm can be led into said second arm.